Expandable shaft apparatus

ABSTRACT

An expandable shaft for gripping an inside surface of the axial hole of a cylinder such as a spool or like object. Shaft diameter variation is achieved through use of several pairs of eccentric rings positioned as a core shaft. Each pair of rings consists of an inside eccentric ring attached to the core shaft and an outside eccentric ring mounted on the first ring with a freedom of motion for a relative rotational displacement with respect to the first ring which results in variation of the overall outside shaft diameter at a particular point on the circumference. By using a number of eccentric ring pairs and arranging them about the core shaft, the outside shaft diameter can be made to expand to the truc geometric center of the cylinder axial hole.

mite States Patent Fredrickson 1 Oct. 30, 1973 EXPANDABLE SHAFT APPARATUS Primary ExaminerGeorge F. Mautz [76] Inventor: David L. Fredrickson, Brainerd, Ass'smm f"" mhons Minn Attorney-Wicks and Nemer [22] Filed: Oct. 20, 1971 Appl. No.: 191,032

[57] ABSTRACT An expandable shaft for gripping an inside surface of the axial hole of a cylinder such as a spool or like object. Shaft diameter variation is achieved through use of several pairs of eccentric rings positioned as a core shaft. Each pair of rings consists of an inside eccentric ring attached to the core shaft and an outside eccentric ring mounted on the first ring with a freedom of motion for a relative rotational displacement with respect to the first ring which results in variation of the overall outside shaft diameter at a particular point on the circumference. By using a number of eccentric ring pairs and arranging them about the core shaft, the outside shaft diameter can be made to expand to the true geometric center of the cylinder axial hole.

9 Claims, 10 Drawing Figures 7 PATENIEDHM 30 ms SHED" 10? 2 INVENTOR. DAVID L. FREDRICKSON Arroawsvs SHEET 2 BF 2 PATENTED UN 3 0 I975 INVENTOR. DAVID L. FREDRICKSON FIG. 68

FIG. 6A

ATTORNE YJ EXPANDABLE SHAFT APPARATUS FIELD OF THE INVENTION The present invention pertains to shafts for gripping the axial hole of a cylinder, such as a spool of paper or yarn. More particularly, the present invention pertains to shaft which can be radially expanded or contracted for easy insertion and removal from the spool axial hole.

SUMMARY OF THE INVENTION The shaft according to the present invention is capable of expanding and contracting radially such that it can be easily inserted into the axial hole of a spool. Once the spool is placed in position on the shaft, the shaft can be expanded to grip the spool firmly and hold it until it is desired to release it and remove it from the shaft. The invention disclosed here will find a wide field of use, but will be particularly useful in paper manufacturing processes, as well as in the printing and textile industries.

Briefly, a plurality of pairs of eccentric rings are mounted on a core shaft, each pair consisting of an inside and outside ring. The inside ring of each pair is secured to the core shaft for rotation with it, while the outside rings are adapted for relative rotation with respect to the inside rings. Due to the eccentric nature of the rings in each pair, relative rotation of the rings results in an overall outside diameter variation. By arranging the plurality of ring pairs uniformly about the core shaft, rotation of the outside rings in unison results in expansion or contraction of outside shaft diameter at a plurality of points spaced equidistantly about the shaft circumference. The number of points at which the shaft expands or contracts corresponds to the number of pairs of eccentric rings in the set. To hold the spool firmly and in proper axial orientation, two or more sets of ring pairs are used at appropriate separation on the shaft, depending on the width of the spool.

Several advantages are offered by the use of the present invention. One such advantage is that the shaft expands to the true geometric center of a roll because the eccentric pairs of rings expand uniformly in unison at equal angular intervals. For example, if three pairs of eccentric rings are used, the shaft will expand equally at three points on the circumference separated from each other by 120. If four pairs of eccentric rings are used, the separation will be 90, and so on.

Another advantage of the present invention is that during the unwinding of the roll of paper, the shaft is self locking due to the tension in the sheet of paper which is usually maintained by reverse torque applied to the shaft. The frictional engagement between the outside eccentric ring of each pair and the inside surface of the roll axial hole is such as to tend to pull the ring towards the direction of expanding shaft diameter.

Still another significant advantage of the present invention is that, in view of inherent radial symmetry, the shaft can be dynamically balanced.

It is therefore an object of the present invention to provide an improved expandable diameter shaft.

Another object of the present invention is to provide an expandable shaft which expands uniformly to maintain the shaft at the true geometric center of the spool axial hole.

A further object of the present invention is to provide an expandable shaft which is self locking.

A yet further object of the present invention is to proivde an expandable diameter shaft which can by dynamically balanced.

These and further objects will become apparent to those skilled in the art after examination of the following specification, claims, and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded view of a set of three pairs of eccentric rings as they would appear on a shaft;

FIG. 2 is a longitudinal crossectional view of a shaft with a set of eccentric rings in accordance with the preferred embodiment of the present invention;

FIG. 3 is a radial crossectional view of the shaft of FIG. 2 taken at plane 33;

FIG. 4 illustrates a shaft equipped with two sets of three pairs of eccentric rings at two separate locations on the shaft;

FIG. 5 illustrates a torque transfer tube for use in the preferred embodiment of FIGS. 2 and 3;

FIGS. 6A, B and C illustrate the principle of three expanding eccentric ring pairs;

FIG. 7 illustrates an expending shaft with a expanding eccentric ring pairs; and

FIG. 8 shows a radial crossectional view of an expanding shaft according to the present invention engaging the inside surface of a paper spool axial hole. de

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. I, a set of three pairs 10, 11, and 12 of eccentric rings are shown in an exploded view. Pair I0 is comprised of an inside eccentric ring 14 and an outside eccentric ring 15, pair 11 is comprised of an inside ring 17 and an outside ring 18, and pair 12 is comprised of an inside ring 20 and an outside ring 21. A core shaft 30 is shown of a somewhat smaller diameter than the inside diameter of inside rings l4, l7, and 20. A bearing sleeve 31, which may be constructed of low friction plastic, lines the outside surface of the core shaft 30. Mounted on core shaft 30 is a cylindrical torque transfer tube 32 which is illustrated in more detail in FIG. 5 and will be described further below. Torque transfer tube 32 is adapted for rotational displacement with respect to core shaft 30. The outside diameter of torque transfer tube corresponds to the inside diameter of inside rings l4, l7 and 20, which are positioned on it and fastened to shaft 30 through slots hereinafter referred to in torque transfer tube 32. Each of the eccentric rings has an outside circular circumference and an inside circular circumference, whose geometric centers are displaced from each other along an eccentricity axis normal to the axis of core shaft 30.

Positioned between ring pairs Ill and I2 is a torque transfer disc 26. Disc 26 has an inside circular hole corresponding in diameter to the outside diameter of torque transfer tube 32. A torque transfer pin 28 is mounted on the side of the disc 26 nearest ring pair 11 and protrudes from it twoards pair 11 to engage a radial slot 22 in outside ring 18. A similar torque transfer pin (not visible) protrudes from the opposite surface of disc 26 to engage a radial slot 2.3 in outside ring 21, of pair 12, FIG. I.

A torque transfer disc 25, similar to disc 26, is positioned between ring pairs 10 and 11. Disc 25 is also equipped with torque transfer pins engaging radial slots set of six in outside rings and 18 of eccentric ring pairs 10 and 11, respectively.

A torque transfer spacer 27, in the form of a cylindrical tube, is positioned on torque transfer tube 32 adjacent to eccentric ring pair 12 on the side opposite from torque transfer disc 26. Spacer 27 has mounted on it a torque transfer pin 2% for engaging a radial slot (not visible) on outside ring 21 of pair 12. Spacer 27 is further secured to torque transfer tube 32, by means of rivets or screws 35 and 36 shown in FIG. 2, and functions, as the name suggests to transfer the torque from torque transfer tube 32 to outside rings 15, 18 and 21 of ring pairs 10, 11 and 12 through torque transfer discs 25 and 26.

In FIG. 2, inside rings R4, 17, and are shown fixed to core shaft 30 by means of locking pins, 37, 38, and 39, respectively. Locking pins 37, 38 and 39 protrude through torque transfer tube 32 at slots 41, 42 and 43 shown in FIG. 5. Slots 41, 42 and 43 extend along the circumference in planes normal to the core shaft axis for about 180 degrees. By virtue of these slots, the inside rings of the eccentric pairs are allowed to move with the core shaft in relative rotational displacement with respect to the torque transfer tube.

Since the inside rings of the eccentric pair are attached to rotate in unison with core shaft 30, while the outside rings are coupled wth the torque transfer tube 32 by means of torque transfer spacer 27 and torque transfer discs and 26, it is clear that a relative rotational displacement of the core shaft and the torque transfer tube will result in simultaneous relative rotational displacement of the two eccentric rings in each pair.

Also shown in FIG. 2 is a shaft holding collar 44 attached to core shaft and a torque release collar 45 attached to torque transfer tube 32. A plastic washer 46 is placed between collars 44 and 45 to reduce the friction between them and facilitate relative rotation. Expansion and contraction of the shaft can thus be achieved through relative rotational displacement of the two collars.

Inside eccentric rings 14, 17 and 20 are attached to core shaft 39 such that their eccentricity axis (an extension of a straight line connecting the displaced centers of the inside and outside ring circumferences) are separated from each other by 120. Such an arrangement provides for uniform expansion of the shaft at three equidistant points.

Three pairs of rings have been shown in the preferred embodiment. However, this is merely a matter of design choice. For most applications three pairs of eccentric rings will be preferred. For some applications two pairs may be adequate, and for others it may be desired to provide more than three pairs. FIG. 7 shows an embodiment using six pairs. The shaft of FIG. 7 expands at six points on the circumference, separated from each other by 60.

In FIG. 4 an expanding shaft is shown with two sets of eccentric rings, each set comprised of three pairs. The two sets are positioned at locations separated by torque transfer spacer 27. By providing two sets of rings, a true centering of the spool is achieved along the entire spool axis. In some situations a single set may suffice, in other cases it may be desirable to use several sets.

FIG. 6 may be helpful to the understanding of the present invention. It shows in FIGS. 6A and 68 a set of three pairs of eccentric rings in a non-expanded shaft orientation and shows in FIG. 6C the same rings in expanded shaft orientation.

The shaft of FIG. 6C is shown in FIG. 8 within the axial hole of a roll of paper 50. To maintain tension in the sheet of paper, a reverse torque is normally applied to the shaft. The frictional force between the outside eccentric rings and the inside surface of roll axial hole will tend to pull the outside rings in the direction of expanding shaft diameter. Maximum expansion occurs on rotation in either direction. The expandable shaft according to the present invention is therefore self locking, regardless of the direction of shaft rotation.

While the foregoing specification describes the preferred embodiments of the invention, it is obvious that many variations are possible without departing from the scope and spirit of the present invention.

I claim:

1. An expandable shaft apparatus for gripping an inside surface of the axial hole of a cylinder such as a spool or like object, said shaft comprising:

an elongated cylinder shaft bodys a cylindrical torque transfer tube mounted on said shaft body for relative rotation therewith; said torque transfer tube having a plurality of parallel circumferential slots each extending along a portion of the tube circumference;

a set of a plurality of pairs of eccentric rings mounted on said torque transfer tube, each pair of rings consisting of a first inside ring having an inside diameter corresponding substantially to the outside diameter of said torque transfer tube; and a second outside ring whose inside diameter corresponds to the outside diameter of said first inside ring and is mounted on said first ring for relative rotational displacement therewith;

means firmly attaching said inside eccentric rings to said shaft body through said slots in said torque transfer tube for rotation in unison with said shaft body and relative to said torque transfer tube;

means coupling said outside eccentric rings to said torque transfer tube; and

means for rotationally displacing said torque transfer tube relative to said core shaft thereby causing relative rotational displacement of each of said pairs of eccentric rings resulting in variation of overall outside shaft diameter at a plurality of points corresponding in number to the plurality of said pairs of eccentric rings.

2. Apparatus according to claim 1 wherein said plurality of pairs of eccentric rings of said set are arranged about said shaft body such that said plurality of points of overall outside shaft diameter variation are spaced equally about said shaft circumference.

3. Apparatus according to claim I wherein said set of pairs of eccentric rings consists of three pairs positioned such that the points of maximum combined eccentricity of said pairs are separated from each other.

4. Apparatus according to claim 1 wherein n pairs of eccentric rings are arranged about said shaft body such that said points of maximum expansion are separated from each other by 360/n 5. Apparatus according to claim 4 wherein two sets of plurality of pairs of eccentric rings are provided, said sets being separated longitudinally along the axis of said shaft body to provide gripping action on the inside ring of each pair is constructed of plastic and the outside ring is constructed of steel.

9. Apparatus according to claim 1 wherein said means for coupling said outside rings to said torque transfer tube include a torque transfer spacer, torque transfer discs between said pairs of eccentric rings. a plurality of torque pins on said discs engaging and connecting together said outside rings, and means connecting said spacer to said disc and to said torque transfer tube. 

1. An expandable shaft apparatus for gripping an inside surface of the axial hole of a cylinder such as a spool or like object, said shaft comprising: an elongated cylinder shaft body; a cylindrical torque transfer tube mounted on said shaft body for relative rotation therewith; said torque transfer tube having a plurality of parallel circumferential slots each extending along a portion of the tube circumference; a set of a plurality of pairs of eccentric rings mounted on said torque transfer tube, each pair of rings consisting of a first inside ring having an inside diameter corresponding substantially to the outside diameter of said torque transfer tube; and a second outside ring whose inside diameter corresponds to the outside diameter of said first inside ring and is mounted on said first ring for relative rotational displacement therewith; means firmly attaching said inside eccentric rings to said shaft body through said slots in said torque transfer tube for rotation in unison with said shaft body and relative to said torque transfer tube; means coupling said outside eccentric rings to said torque transfer tube; and means for rotationally displacing said torque transfer tube relative to said core shaft thereby causing relative rotational displacement of each of said pairs of eccentric rings resulting in variation of overall outside shaft diameter at a plurality of points corresponding in number to the plurality of said pairs of eccentric rings.
 2. Apparatus according to claim 1 wherein said plurality of pairs of eccentric rings of said set are arranged about said shaft body such that said plurality of points of overall outside shaft diameter variation are spaced equally about said shaft circumference.
 3. Apparatus according to claim 1 wherein said set of pairs of eccentric rings consists of three pairs positioned such that the points of maximum combined eccentricity of said pairs are separated 120* from each other.
 4. Apparatus according to claim 1 wherein n pairs of eccentric rings are arranged about said shaft body such that said points of maximum expansion are separated from each other by 360/n *.
 5. Apparatus according to claim 4 wherein two sets of plurality of pairs of eccentric rings are provided, said sets being separated longitudinally along the axis of said shaft body to provide gripping action on the inside surface of the axial hole of the cylinder at two separate locations.
 6. Apparatus according to claim 4 wherein a plurality of sets of plurality of pairs of eccentric rings are provided, said sets being separated longitudinally along the axis of said shaft body to provide gripping action on the inside surface of the axial hole of a cylinder at a plurality of separate locations.
 7. Apparatus of claim 1 wherein a cylindrical plastic bearing sleeve is positioned between the shaft body and the torque transfer tube.
 8. Apparatus of claim 1 wherein the inside eccentric ring of each pair is constructed of plastic and the outside ring is constructed of steel.
 9. Apparatus according to claim 1 wherein said means for coupling said outside rings to said torque transfer tube include a torque transfer spacer, torque transfer discs between said pairs of eccentric rings, a plurality of torque pins on said discs engaging and connecting together said outside rings, and means connecting said spacer to said disc and to said torque transfer tube. 